Chloroprene adhesive cured with carbon disulfide-alkyl amino-alcohol reaction product



United S William E. Tann, Akron, Ohio, assignor to The Firestone Tire & Rubber Company, Akron, Ohio, a corporation of Ohio No Drawing. Application April 23, 153 Serial No. 350,753

15 Claims. (Cl. 260-795) This invention relates to improved neoprene (rubbery chloroprene polymer) cements and more particularly to vulcanizable neoprene cements containing a combination of stabilizing agents and vulcanization accelerators as specified herein. The term cements as used in this specification include coatings, paints and adhesives wherein a chloroprene polymer is dissolved or dispersed in a non-aqueous solvent.

Neoprene air-curing cements until the present invention, underwent great increase in viscosity to attain a gelled state during storage before use. This gelled state was due to cross linking produced by curing agents, polymerization oxidation or by mechanism not completely understood. In any event such a gelled state renders the neoprene cement entirely useless for bonding surfaces. Gelling of neoprene cement during storage has been res atent O f avoided before the present invention by manufacturing the cement in two parts and storing each part separately. A nonvulcanizing solvent base cement portion wasformed of neoprene and modifying ingredients such as zinc oxide" and carbon black dispersed in a solvent but withouta vulcanization accelerator.

The base cement portion and f the accelerator portion were stored separately until .ultimate use. Whereupon the base cement andthe-accel-,

erator portion were mixed and the resulting vulcanizable cement was applied immediately to surfaces to'be bonded.

Such two-part cement is cumbersome to store, ship and] use. Moreover such cement is unsatisfactory particularly because in the event that all of the vulcanizable adhesive is not used immediately after the accelerator is added the portion not so used will gell and thus become unusable.

A proposal has been made to reduce the gelling tendency of neoprene cements by reducing the amount of vulcanization accelerator used therein. In order to form a satisfactory bond between two cemented surfaces it is necessary to vulcanize the cement; however, the use of a less' quantity of accelerator requires that the step of vulcanizing the cement be increased an undersirable length of time. Moreover, a reduction of the amount of accelerator in a cement reduces the strength. of thevulcanized bond formed by such a cement.

The most successful of the prior art neoprenetcements to resist gelling is compounded with a vulcaniza:

tion accelerator combination of dibenzylamine andcarbon disulfide. This cement, although havingsome' resistance to gelling for short periods of time, has a very slow rate of vulcanization and for that reason isunsuitable for most applications, particularly those requiring fanfair curing cement.

An object of the present invention is'to provide a neoprene cement which will not gel under normal conditions of storage but which has a rapid 'rate'of vulcaniza- 2,822,352 Patented Feb. 4, 1958,

A further object of the invention is to provide a neoprene cement resistant to gelling during storage but capable of producing a stronger vulcanized bond between two surfaces in reduced vulcanization time.

Yet another object of the invention is to provide an improved neoprene cement which contains as an accelerator the reaction product of an amino-alcohol and carbon disulfide.

The aminoralcohol of. theinventionmay be selected. from the alkylamino-alcohols such as monoethanolamine, diethanolamine and triethanolamine. Other satisfactory amino-alcohols are. monopropanolamine, dipropanolamine and tripropanolamine as well as mixtures-of the propanolamines with each other and other amino-alcohols. Also useful are butanolamines such as isobutanolamine and other amino-alcohols such as 2-amino-2-methyl propanol.

The amino-alcohol or mixture of amino-alcohols selected for the novel cement is mixed with carbon disulfide either before or after addition to the cement.

' In one manner of preparing a cement of the invention, neoprene is masticated on a two-roll mixing mill,'and ingredients such as carbon black, antioxidant, and oils are added with continued mastication until a uniform clispersion of ingredients in the neoprene is obtained. The neoprene compound is removed from the mill and is dis-' solved by stirring in a suitable solvent, such as toluene, until a cement of a concentration approximating one pound of neoprene compound for each gallon of cement is produced. Other methods of mixing are familiar to those skilled in the art of manufacturing solvent cexylene and their homologues; ethylene dichloride, tri- .chloroethylen e, and other chlorinated hydrocarbon solvents; ester solvents, such as amyl acetate, butyl forma-te, butyl acetate, ethyl acetate and ethyl propionate; ketones,

such as methylethyl. ketone, isophorone and thelikeg" mixtures of any of the above solvents with each other or with gasoline or the like; and commercial mixed solvents for neoprene known to the art. V I

The cements of the invention are tested in the following manner: p

' OVEN TESTS A container holding a sample of the cement to be tested is placed in an atmosphere of hot air at 158 F. andthe'time required for the appearance of a solid gel formation in the cement is recorded.

. DEAD WEIGHT TEST The surfaces of two strips of rubberized fabric 12 x 4 A- inches are cleaned with ah aromatic solvent and a margin of at least of an inch along one long edge of each strip is cemented with the neoprene adhesive to be tested.

. The adhesive is allowed to dry and a'second adhesive coatis applied andalso, allowedtodry. ,The. twostrips of;

fabric-are pressed together to form a; inchove rlappin g fs'eamwhich is rolled out with a.roller stitcher; to produce intimate. qnt a fifth? i emeated su faces: a to expel Iilfair f bubbles. The seams f thus formed are air-cured at a:

j n esfio t egs em. The estspe'cimen- 11s desired c atura prthe len th. o utimeuq the test- Samp le specimens two inches in width are cutjat-right placediin an atmosphere of hot r at F. and grlppedzparallel' -t0 th s e ani w ith selflaligning' grips; load is applie'd to the grips -n0rmalto the'seam at a rate of-30 pounds per 'rfninu't'. lin' arr attempt to. 51111 :theseam. apart? .Resultsi. are reported in pounds of load and in time in minutes and seconds'required for separation of the'seam. Ap

paratus for the test is similar to that shown in Figure 4 of United States Air Force-Navy Aeronautical Specification MlL-C-5539 dated January 9, 1950. This specification requires an air drying-adhesive to cure. within ten The above examples show that a satisfactory cure is obtained in an air-cure cement accelerated with aminoalcohol and carbon disulfide. Some amino-alcohols provide an air-curing cement with a more rapid rate of cure days and to have a miuimumstrength on .deadiweight test. 5 than others, i. e. the cement accelerated with isobutanol of 601bs. when tested at 140 F; t 1 amine cures more rapidly than the cement cured with To carry out the invention, a base stock was mixed on a triethanolamine. two-roll rubber milltaccording to the following formula: Only relatively small proportions of the amino-alcohol Pans of weight ofrrubber and carbon disulfide based upon the neoprene content polychlorobutadiene rubber 1 100m tth c n of h invention are qui d- T e ac al Carbon black 3.00 amounts of these ingredients utilized, are in line; with Ann-oxidant 2.00 the amounts of vulcanization accelerators normally. em-

ployed in neoprene cements. Excess carbondisulfide is 105.00, unnecessary-in the cement when the reaction product of Ne Ten CG W d but AC neo mm (W carbon disulfide and the alkyl amino-alcohols are used. s}; i KNB i i f gggg i g e Excess carbon disulfide might be desirable to accelerate The mixed stock was dispersed in toluene to make a i i i m i ffi d base cement with a total solids concentration of approxic oroprene p0 ylner use gamma y matly 10% by weight To this base cement various herein, to include all commercial neoprenes. The term amounts of curing ingredients were added and dispersed, to Include homopolymer? of Chloroprene as Well and the resulting cements were tested in the oven test as copolymers of chloroprene f m" and/or P or and dead weight test, all samples being air-cured at room mom unsaturated Comonomers, mcludmg polymerlable temperature. The added ingredients and test results are 9 Compounds, SuCh a tyrene,acrylon1tr1le, vinylgiven in Example L In the examples Set out all parts pyridine, vinyl chloride, vmyhdene chloride, chlorotrif ingredients are b d on 100 parts f momma 1 fiuoroethylene, and derivatives of these substances as To test the characteristics of novel cements using the W l as th r kn wn mon m rs f the aliphatic and accelerators of the invention, samples were mixed and aromatic series of compounds; a conjugated diene, such tested according to the following example: as butadieue, isoprene, dichlorobutadiene and other Example I 7 Sample No.

Base Cem n Controll lgal lgal lgal. Zinc butyl xanfhnte 5. 9 Dlbenzyl min 6. 16 Carbon disulfide 14.00 Monoethanolammonium ethanoldithiocai-hammo 5 92 11.95. Dead Wt. Test (48 hrs. cure at 75 F.): (cure I 22 hrs. at 75 F.) Pounds 20 a2 58.

Ime-

Min 0 1 1 1. Sec- 4 4 56. 'I'imetogel F 24h No gel,.60 No geLfiO No gel,60

days. days. days.

It will be seen that the use of the reaction product of monoethanolamine and carbon disulfide as an accelerator known polymerizable dienes; and also polymerizable unconjugatedpolyenes, including pentadiene-1,4 and the in cement samples 2, 3 and 4 resulted in increased rate 50 like.

of cure and improved gel resistance over the control.

In addition to monoethanolamine, cements containing diethanolamine and triethauolamine are within the scope of the invention as are cements containing other alkyl amino-alcohols as shown by the following example:

Example 2 g I claim:

1. A quick-curing cement containing a rubbery chloroprene polymer, a solvent for said polymer, and as an accelerator relatively small proportions of the reaction product of carbon disulfide and an alkyl amino-alcohol.

Sample No.

2. A quick-curing cement according to claim 1 wherein the alkyl amino-alcohol is monoethanolamine.

3. A quick-curing cement according to claim 1 wherein the alkyl amino-alcohol is diethanolamine.

4. A quick-curing cement according to claim 1 wherein the alkyl amino-alcohol is triethanolamine.

5. A quick-curing cement according to claim 1 wherein the alkyl amino-alcohol is isobutanolamine.

6. A quick-curing cement according to claim 1 wherein the alkyl amino-alcohol is 2-amino-2 methyl-propanol.

7. A method of manufacturing a quick-curing rubbery chloroprene cement comprising the steps of dissolving the rubbery chloroprene in a solvent, and adding as an accelerator relatively small proportions of the reaction product of an alkyl amino-alcohol and carbon disulfide.

8. A method of manufacturing a quick-curing rubbery chloroprene cement comprising the steps of dissolving the rubbery chloroprene in a solvent and adding as accelerators relatively small proportions of an alkyl aminoalcohol and carbon disulfide.

9. A quick curing cement containing a rubbery chloroprene polymer, a solvent for said polymer, and as an accelerator the reaction product of an excess of carbon disulfide and not over 8.1% of an alkyl amino-alcohol based on the weight of said polymer present.

10. A quick curing cement according to claim 1 wherein the alkyl amino-alcohol is monoethanolamine.

11. A quick curing cement according to claim 1 wherein the alkyl amino-alcohol is diethanolamine.

12. A quick curing cement according to claim 1 wherein the alkyl amino-alcohol is triethanolamine.

- 13. A quick curing cement according to claim 1 wherein the alkyl amino-alcohol is isobutanolamine.

14. A quick curing cement according to claim 1 wherein the alkyl amino-alcohol is 2-amino-2 methyl-propanol.

15. A method of manufacturing a quick curing rubbery chloroprene cement comprising the steps of dissolving the rubbery chloroprene in a solvent and adding as accelerators not over 8.1% based on the weight of polymer present of an alkyl amino-alcohol and an excess of carbon disulfide.

References Cited in the file of this patent UNITED STATES PATENTS 2,024,925 Hirschkind Dec. 17, 1935 2,163,611 MacDonald June 27, 1939 2,340,650 Dean Feb. 1, 1944 2,372,895 Harman Apr. 3, 1945 2,455,911 Bake Dec. 14, 1948 2,514,192 Tann -1 July 4, 1950 2,525,200 Bergmann Oct. 10, 1950 2,649,432 Little Aug.18, 1953 

1. A QUICK-CURING CEMENT CONTAINING A RUBBER CHLOROPRENE POLYMER, A SOLVENT FOR SAID POLYMER, AND AS AN ACCELERATOR RELATIVELY SMALL PROPORTIONS OF THE REACTION PRODUCT OF CARBON DISULFIDE AND AN ALKYL AMINO-ALCOHOL. 